Vaccines against various and evolving strains of influenza are important not only from a community health stand point, but also commercially, since each year numerous individuals are infected with different strains and types of influenza virus. Infants, the elderly, those without adequate health care and immunocompromised persons are at special risk of death from such infections. Compounding the problem of influenza infections is that novel influenza strains evolve readily, thereby necessitating the continuous production of new vaccines.
Numerous vaccines capable of producing a protective immune response specific for such different influenza viruses have been produced for over 50 years and include, e.g., whole virus vaccines, split virus vaccines, surface antigen vaccines and live attenuated virus vaccines. However, while appropriate formulations of any of these vaccine types are capable of producing a systemic immune response, live attenuated virus vaccines have the advantage of being also able to stimulate local mucosal immunity in the respiratory tract. A vaccine comprising a live attenuated virus that is capable of being quickly and economically produced and that is capable of easy storage/transport is thus quite desirable. Even more desirable would be such a vaccine that would be capable of storage/transport at refrigerator temperatures (e.g., approximately 2-8° C.).
To date, all influenza vaccines commercially available in the U.S. have been propagated in embryonated hen eggs. Although influenza virus grows well in hen eggs, the production of vaccine is dependent on the availability of such eggs. Because the supply of eggs must be organized, and strains for vaccine production selected months in advance of the next flu season, the flexibility of this approach can be limited, and often results in delays and shortages in production and distribution. Therefore, methods to increase stability (e.g., at refrigerator temperatures) of the produced vaccine, are greatly desirable as they can prevent deterioration of vaccine stock, which would otherwise necessitate new production, etc.
Systems for producing influenza viruses in cell culture have also been developed in recent years (See, e.g., Furminger. Vaccine Production, in Nicholson et al. (eds.) Textbook of Influenza pp. 324-332; Merten et al. (1996) Production of influenza virus in cell cultures for vaccine preparation, in Cohen & Shafferman (eds.) Novel Strategies in Design and Production of Vaccines pp. 141-151); therefore, any methods to increase vaccine composition stability (e.g., storage/transport at refrigerator temperature) in these systems as well are also greatly desirable.
Considerable work in the production of influenza virus for production of vaccines has been done by the present inventors and co-workers; see, e.g., U.S. patent application No. 60/375,675 filed Apr. 26, 2002, PCT/US03/12728 filed Apr. 25, 2003, U.S. Ser. No. 10/423,828 filed Apr. 25, 2003, and PCT/US05/017734 filed May 20, 2005.
The present invention provides vaccine compositions that have stability at, for example, refrigerator temperatures (e.g., 4° C.) and methods of producing the same. Aspects of the current invention are applicable to traditional hen egg and new cell culture vaccine production methods (and also combined systems) and comprise numerous other benefits that will become apparent upon review of the following.